Slides in this set

Slide 1

Slide 2

Primary Defences Skin This acts as a physical barrier blocking pathogens from entering the body. It can also act as a chemical barrier by producing chemicals that are antimicrobial and can lower the pH, inhibiting the growth of pathogensMucous membranesThey protect body opening that are exposed to the environment (such as mouth, nostrils, ears) Somemembranes secret mucus ­ a sticky substance that contains antimicrobial enzymes. The epitheliallayer in the lungs contains mucus secreting goblet cells. Most pathogens in the digestive system arekilled by the acidity of the stomach which can be 1-2 pH This denatures the pathogens enzymes.The eyes are also protected by antibodies in tear fluid.…read more

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Phagocytosis ­ a secondary defence 1) A phagocyte recognises the antigens on a pathogen 2) The cytoplasm of the phagocyte moves around the pathogen, engulfing it 3) The pathogen is now contained in a phagocytic vacuole ( a bubble) in the cytoplasm of the phagocyte 4) A Lysosome fuses with the phagocytic vacuole. The digestive enzymes break down the pathogen 5) The phagocyte then presents the pathogen's antigens. It sticks the antigens on the surface to activate other immune system cells.There are two types of phagocyte;· Neutrophils; the most common type, are manufactured in the bone marrow. They travel in theblood and often squeeze out into the tissue fluid. Neutrophils are short lived but are released inlarge numbers as a result of infection.·Macrophages; are larger cells also manufactured in the bone marrow. The travel in blood asmonocytes. They tend to settle in the lymph nodes. Here they develop into macrophages.…read more

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AntibodiesAntigens are molecules that stimulate an immune responseAntibodies are protein molecules that can identify and neutralize antigens The structure of an Antibody ·Four poly peptide chains held together by disulphide bridges ·A constant region which is the same in all cells this allows the antibody to attach to the phagocytic cells, helping the process of phagocytises ·A variable region which has a specific shape. This is a result of its amino acid sequence. It ensures that the antibody can attach to the complementary shaped antigen. ·Hinge regions which allow a degree of flexibility. These allow the branches of the Y shaped molecule to move apart so they can attach to more than one antigen.…read more

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How antibodies workAgglutination Agglutination A large antibody, which resembles several Y shaped molecules attached together with severable variable regions, can bind many pathogens together. The group of pathogens is now too large to enter the host cell.NeutralizationMost Antibodies cover the pathogenbinding sites to prevent the pathogenfrom binding to a host cell and enteringthe cell…read more

Slide 6

Producing Antibodies Antibodies are produced in response to an infection. However it takes a few days for there to be enough antibodies in the blood to combat the infection. This is known as the primary immune response. Once the pathogens have been dealt with the number of antibodies drops dramatically. If the body is infected by the same pathogen, the antibodies must be made again. But the immune system can swing into action more quickly. The production of antibodies starts sooner and is much more rapid. The concentration of antibodies rises sooner and reaches a higher concentration. This is known as secondary immune response.…read more